I like the convenience of working out at home. The upside is that once you eliminate the travel time to a gym, a lot more opportunities to exercise open up. The downside is that, 90 percent of the time, those opportunities never seem ideal for one reason or another, and the home gym equipment gathers dust in the guest bedroom.

If you'd like to exercise at home but want to select equipment that won't suffer that fate, the following guidelines might help.

Rent equipment before buying

Rent the item you're considering or try it at a gym first to be sure you'll spend time on it. With gym equipment, you truly get what you pay for. If you can't afford high-quality new equipment, look for a high-quality used piece. And before buying, make sure the store will allow you to exchange it.

Treadmill: If you're interested in running or walking, treadmills work well. In fact, in some cases, treadmills work better than running or walking outdoors. You can control your pace on a treadmill, which can protect you from opening your stride too much (important if you suffer from hamstring injuries), yet you still get the hip extension and knee flexion of a good running workout. A treadmill is also convenient; it's no fun to be 5 miles out on a run, feel a twinge and have to limp home. And they're low impact, so treadmills provide a good running bed if you plan to run for an extended period of time — say, if you're training for a marathon. If impact is a big issue for you, anti-shock treadmills are available from several companies, including Precor, Nautilus and Technogym.

Elliptical: An elliptical (a cross between a stationary bicycle and a treadmill) is a good choice if you need to minimize joint forces.

Cycling trainer: If you're interested in cycling, consider a wind trainer, which lifts the rear wheel of your bicycle, making it stationary. For general fitness, wind trainers are ideal: You optimize your exercise time while also eliminating outdoor hazards such as cars, dogs, potholes, rain, snow, sun exposure, heat and humidity. They're also perfect for interval training because you can gauge each interval exactly — no wind or changing terrain to vary each interval. Downside: You miss out on honing your bike-handling skills.

For even more sophisticated indoor cycling, add a CompuTrainer — a computer-aided training device that offers you variable resistance as well as feedback on your speed, power, cadence, heart rate and RPMs. You can also get software to run on your computer while you ride your CompuTrainer, which will allow you to race friends or race on a course simulating world championships, the Tour de France or the Race Across America.

Universal trainer: If you're in the market for a universal-type gym device, pay special attention to the machine's resistance throughout the range of each exercise. Those that use pulley systems with springs or elastic bands can have heavy resistance at the start of the lift but light resistance at the end. Spring-loaded systems can be light at the start but get heavier toward the finish. You want to find one with consistent resistance throughout the lift.

Entice yourself

To ensure your home gym equipment stays dust-free, set it up near a TV, or get a book holder so you can sweat it out while reading your favorite book or newspaper.